Best Under Sink Water Filter Reviews and Buying Guide 2021

What is the Best Under Sink Water Filter? 

The under sink water filter technology was one of the first ones, along with reverse osmosis, to come into the market.

There are many filtration options out there, from small Brita filters, up to large whole-house systems that filter everything as required.

How are we going to decide what is best?

To give you the best information, we have reviewed five (5) top products in the mid-sized category of under sink water filtration system.

For this, we will talk about:

  • what they filter out, what they don’t, and how much maintenance they need.
  • their quality of components.
  • What they do best against the competitors.


Doulton Ultracarb Alkaline Filter – Best in Providing Minerals

Doulton Ultracarb Alkaline Filter - Best in Providing Minerals

  • Filters 99% of micro-organisms.
  • Filters acidifying particles leaving the good ones for your body to absorb.
  • Easy to maintain and effective against growing bacteria.


  • Only 600 gallons capacity (2.27 cubic meters); still great for your water needs.
  • It is a little bit pricey but this means good quality.

This Dulton Ultracarb is a two (2) cartridge filtration system, which is a little different than our previous entries.

The first cartridge contains ceramic and a silver infusion layers.

The ceramic layer will remove micro-organisms such as Cryptosporidium (parasite), small particles, organic compounds, chlorine and, heavy metals such as lead.

To refine the quality of the water filtered, there second layer of silver infusion will ensure there is no bacteria growth.

The secondary cartridge will improve the quality of minerals contained in the water.

In order to provide the right amount of minerals in the filtered water, the alkaline process will increase the pH of the water by separating and removing acidifying particles through electrolysis.

This leaves the antioxidants, improving the flavor of the water and helping the abortion of minerals by your body.

This filter is only rated for 600 gallons of total capacity. This may seem low, but this is specifically a drinking water filter.

Now, I recommend you use it only for drinking potable water or washing vegetables. This way, you can maintain the lifespan of the filters.

The reason behind my advise if because the filters are a bit small so they will get clogged easily overtime.

I guess one of the best advantages of the system is the “faucet ready” approach, which includes all the elements for easy installation.

Not the one you are looking for? Keep on reading the next review.


Aquasana AQ 5300 – Best Max Flow

Aquasana AQ 5300 3-Stage Max Flow Under sink water filter

  • Three (3) filtration stages to ensure most contaminants are removed.
  • It comes with a faucet ready to be installed.
  • Flow rate delivered is excellent considering the number of stages involved.
  • It can remove PFOS from the water.

  • The lifespan is low even with the filters size.
  • Not ideal for kitchens with a small under sink area.
  • Filters could be a little hard to remove for replacement.

The AQ 5300 is an under sink filter designed and manufactured to provide a descent amount of water on the go.

Not many systems in this category have a three (3) stage process. That is the main reason this Aquasana model is not a bad choice.

Although, this is the case, having a few stages makes it land on the expensive side too.

Why? Well, even if the cartridges are separated from each other, you should be replacing all of them at the same time.

Unfortunately there is no way to do a backwash, which usually increases the usability of a filter.

If you find a way to backwash the filters, please comment because I wan to know.

If you have limited budget, I would suggest to get a descent faucet water filter that can provide the same filtration lifespan.

To me, the Aquasana 5300 Max Flow is a great alternative just for the sake of the amount of pollutants that can be removed from the municipal water supply.


Woder 10K Gen3 – Best Small Kitchen Under Sink Water Filter

Woder 10K-Gen3 water filter

  • Important components for your body hydration are left in the water.
  • Very easy to install (directly to your cold water line).
  • It is capable of filtering 10000 gallons of water.

  • Does not filter heavy metals.
  • Only filters municipal water (disinfected).
  • Fluoride is not removed by the filter.

The Woder 10K Gen3 filtration system was designed to remove harmful contaminants without reducing the mineral content of your water.

Having said that, it specifically does not filter out calcium, potassium, sodium, magnesium or phosphorus, which are essential for bodily functions.

Of course, it will filter harmful contaminants such as:

  • Organic compounds and chlorine.
  • Heavy metals including but not limited to lead, mercury and Cr6+ (very dangerous element).
  • Most inorganic compounds.

This filter is rated for three (3) years or 10,000 gallons lifespan.

With that in mind, it will last far shorter if you use it for well water, due to heavy mineral content and other potential contaminants.

From what I can see so far, this inline configuration could make this Woder water filter a budget friendly alternative.

Aside form the above, I love the simplicity of its design. For a beginner installing a filter, it would be like a walk in the park.

Be mindful of the hoses attached to it. They are 3/8” supply lines so make sure your kitchen connections have the same diameter.

Lastly, as I have mentioned, I reckon this would be the perfect fit for any small kitchen do to its compact design.

Further down this article, you will find the technical aspect of this Woder filter.


Apec WFS 1000 – Best Alternative for Well Water

Apec WFS 1000 3 stage system

  • It is suitable to filter well water if that is what you have.
  • Each filter is easy replaceable and are not inter-dependent.
  • Much more contaminants removed per square meter.

  • Its medium size could be not the ideal fit for small kitchens.
  • The first filter (stage 1) gets clogged easy.
  • Apparently, the installation process is not too straightforward.

If you know the water you want to filter is heavily impacted with harmful contaminants, the Apec WFS 1000 could be the alternative you need.

Although, its dimension (15.24 x 38.1 x 30.48 cm) are not exactly the ideal ones for a small kitchen, the large filters have been designed to last for more than the usual six (6) months.

This also take us to the weight issue. It is possibly heavy to hold its weight for some time while installation.

We know the quick connect fittings are great for a fast installation and troubleshooting, nevertheless this could be a strong plumbing limitation for some users.

Lastly, the filtration of water coming from a well. This Apec model will do the job as long as the Total Dissolve Solids (TDS) concentration is not absurd.

Get a water test from your local store to know what the TDS is.


CuZn UC 200 Under Counter Water Filter – Best Filter Lifespan

CuZn UC 200 under counter water filter

  • Its inline filter was built to filter 50000 gallons.
  • Installation is super easy.
  • Three (3) media layer to remove more contaminants than other competitors.

  • Water with high level of TDS can be filtered.
  • If you need a new filter, you will need to replace the whole thing.
  • Possibly not suitable for small kitchen, even if its an inline configuration.

The CuZn UC 200 is another inline water filter that has an impressive lifespan.

As its name says, copper (Cu) and zinc (Zn) are used in combination to remove greater number of pollutants including hydrogen sulfide.

Most importantly, this combination reduces bacteria growth.

I guess what makes it great is its actual size, which should be very suitable for medium to large kitchen sink areas.

Unfortunately, its 38 cm (15″) makes it not an alternative for limited space in some kitchens.

What I love most is the cost – benefit of this filtration system. So far, no other under sink filter manufacturer has provided such a high filtration capacity.

For the reason above, that is why you will be disposing the whole unit (you can keep the hose) when replacement is required.

The only thing is not clear for me is how it can last so long if it almost has the same configuration as other low lifespan filters?

I guess the count that you will only use it for municipal water sources with very low TDS.

A Quick Buying Guide to Under Sink Water Filters in 2021.

We all want clean water for our daily needs, right?. This often means installing a good filtration system but not always is the right fit for what is required.

If you want to learn more about the under sink water filter world, this buying guide will provide all the information needed to help you find the best one for you.

Lets start with some of the basic concepts.

How Does an Under Sink Water Filter Work?

Basically, as its name suggests, these water filters are installed under your counter.

Your water is filtered on-demand, as this system is incorporated into your original sink plumbing.

In order to make the water run through the cartridge’s, you have to have a descent water pressure.

You can tell that this configuration are very similar to RO filtration systems, but less sophisticated.

Normally you should have a water pressure supply between 20 psi and 85 psi. Less than that may not be ideal for systems with a few filtration stages.

With the right conditions and installation, you will have a steady flow of clean water.

How to Install an Under Sink Water Filter?

Not all the available systems are easy to install. Some of the reason are:

  • Not enough under sink space.
  • Most of them require to be embedded to the wall.
  • The faucet and hose fittings may not have similar specification to some standard kitchens.

The basic approach for an easy installation of an under sink filter is to:

  • Measure the available for the filters to fit.
  • Check the dimentions (height and width) of the whole system and compare to your kitchen under counter space.
  • If all ok, install the main structure to the cabine’s wall and attach the water hoses to the water tap supply.
  • The last step is to connect the cartridges to the already installed structure.

Some users prefer to put together the whole filtration system before doing any plumbing works. That is ok too but may be a bit bothersome to hold the weight of it.

What is the Main Technology Used for Under Sink Water Filtration Systems?

Each manufacturer is very cautions with the filtration media used. This is, in most cases, the breaking factor on buying from one supplier or another.

Commonly cartridges with activated carbon technology is used as part of this filter system.

However, in modern filtration systems, it is more common – and a good idea – to have a combination of filters to eliminate more contaminants.

For example, when a special alumina filter is incorporated, then these water filters can also remove fluoride and arsenic.

Some other expensive, but ideal, systems offer bacteria growth control and remineralization.

Any expert in this field will suggest to test the water of your supplier before buying any water filtrations system.

This is important to do since you must know and understand what contaminants you are dealing with.

Benefits and Limitation

So far we have a total of six (6) water filtration systems that you can select from.

But not all of them will have the same benefits as some under sink water filters. These are some of its pros:



  1. They can provide good water flow during filtration.
  2. No countertop clutter. The entire unit is stored under the counter.
  3. Compared to RO systems, no waste water is produced.
  4. There are some models with an inline configuration that are perfect for small kitchens that required high water demand.
  5. Easy maintenance routine! You just need to keep on top of cartridge replacement.

All of the above sounds good but there are some limitation that you should know:



  1. They require a minimum of 20 psi of water pressure for optimal operation.
  2. Although, it is not very difficult to install, you still have to do some slight works such as drilling holes to hang the system.
  3. It has high filtration capacity but not all contaminants are removed.
  4. It could be hard to undo a cartridge without removing the whole structure out of the sink.
  5. Most of these systems last for 6 months (maybe 1 year tops), which could be not so cost effective.

Types of Under Counter Water Filters

Now, let’s consider this filtration system in more detail. There are two (2) types: the conventional parallel configuration and the simple system (inline).


Conventional Under Sink Water Filter

This system was the initial design for a under sink water filter.

Conventional under counter filterThe main characteristic is that it requires a separate faucet for dispensing the filtered water.

You would reroute some of your cold water supply (point A) through this filtration system via a connection.

Once your water is filtered (point B), you access it via the separate faucet.

You would still have cold and hot water flowing unfiltered from your usual faucets.


  1. Cartridge replacement frequency is low. Since you only filter a portion of your cold water supply, each cartridge lasts longer.
  2. Better water quality. Usually there is a minimum of two (2) parallel filters.
  3. Water flow is based on the municipal supply pressure.


  1. More hardware! The vast majority of systems will require to use a separate faucet.
  2. Kitchen alterations required. You will need a sink with dual faucet holes. Alternatively, you can drill a new hole in your existing sink.
  3. It may not be suitable for small kitchens.


Inline Under Sink Water Filter

Inline under counter water filter

An inline water filter is the alternative you need if you don’t have enough space under the sink.

Similar the its counterpart, it has to be connected to the cold water supply, not the hot one.


  1. There’s no need for an extra faucet as it gets connected to the main water supply outlet.
  2. No need to mess with your kitchen design! There is zero need for drilling any holes (you can do if you want though).
  3. Cost effective in the long run as you only need to buy one cartridge.
  4. It is super easy to install and all the elements required are included.


  1. There could be a slight reduction of the water pressure. This means, you will need a minimum of 30 psi of pressure to have a descent flow.
  2. It may require more maintenance than usual. This includes replacing cartridges more often.
  3. Some models have a standard hose diameter inlet/outlet so you will need to check that they match your kitchen connection points.

Buying the Right Under Counter Water Filtration System

We have seven (7) reasons why you should study more in detail the importance of selecting the best under sink water filtration system before investing.


Kitchen space

You should first, figure out if there is enough space under the sink, this includes taking detailed measurements.


Home usage profile

You need to know the volume of water required to satisfy your family’s usage profile.

Even though we suggest to think about that, this filters are good enough to supply any quantity of water.


Treatment requirements

Another important step is to know the contaminants present in the water you are drinking.

As mentioned before, each manufacturer has different filtration media to remove or reduce certain contaminants.

This is possibly the MOST IMPORTANT POINT TO CONSIDER, since even maybe an under sink water filter may not suffice to treat the water.


Efficiency vs. cost

While you want a great water filter that produces perfectly clean water, also pay attention to the cost.

Higher efficiency means a higher cost.

This is a trade-off that you will need to balance as you select the best model for your budget and requirements.

The good news is that this type of water filtration system tends to be affordable in many ways.


Minimum required water pressure

Have clean water is good, but to access it when you need it, is far better.

Select a filter model that can handle your home’s water pressure.

Inline under sink water filter systems tend to handle higher water pressure due to their hose diameter.

This translate to more flow rate and less waiting time to fill up a glass or a jug.


Cartridge replacement rate

Your water filter is only as good as its cartridges. Longer lasting cartridges with the capacity to handle larger water volumes are more ideal.

Depending on the selected model, you may need to replace the cartridges twice per year (every six (6) months).

This depends on the concentration of contaminants in the water and the usage of the system.

However these replacement time frames are only suggestions. If your water supply requires more filtration, then your system will be heavily taxed.

You may need to replace the cartridges more frequently than stated so consider possibly another water filtration system.



How complex is the installation of the under sink water filter you want? Usually they are not complicated to install but it requires a but of ability.

There are some videos you can look at as a guide but honestly, that is not required.

If you still can’t get it done with that extra info, then call in a professional plumber for the installation.

Best Under Sink Water Filter Summary

Now that we have stated our point of view of the best under sink water filters in 2021, this summary table also contains the technical aspects of each model:

NameAquasana AQ 5300 3 Stage Max Flow Aquasana AQ5300 under sink water filter review - ACWCuZn UC-200CuZn UC-200 - under sink water filterApec Water WFS 1000Apec Water WFS-1000 water filterWoder 10K-Gen3Woder 10K-Gen3 water filterDoulton Ultracarb 0.5 Micron 10” (Alkaline)
Doulton Ultracarb 0.5 Micron 10” 2-stage water filter (with Alkaline)
Main FeaturesRemoves up to 99 percent of 77 pollutants present in municipal waters.Filters up to 50000 gallons, enough for a big family.Removes common contaminants and is under an affordable price compared to other filters.Long lasting filter removing important contaminants such as heavy metals.The Alkaline filter offers high benefits for your water taste and more importantly, for your body mineral requirements
Pollutants Removed- Heavy metals.
- Herbicides & Pesticides.
- Bacteria and asbestos.
- Heavy metals such as lead, Cr6+, mercury, cadmium and others.
- Herbicides and Pesticides.
- Bacteria and micro particles (not Total Dissolve Solids).
Sediments, organic and inorganic compounds, heavy metals and chlorine.Organic compounds, heavy metals, chlorine and sediments.- Heavy metals such as Lead.
- Micro-organisms such as parasites and small particles.
- Organic compounds & Chloride.
- Acidifying particles.
Flow rate0.5 GPM (2.0 lpm).2 GPM (12.6 lpm).0.72 GPM (2.7 lpm).2 GPM (12.6 lpm)0.5 GPM (1.89 lpm).
Water Pressure (Optimal - PSI)20-80.65.20-85.65.10-125.
Size/designMedium / Eco-friendly.
12 x 4.2 x 9 inches.
Small to medium size.Medium to large size.Small sizeMedium size
Filters made of- Pre-filter
- Activated Carbon.
- Catalytic Carbon with Ion Exchange.
- Coconut shell carbon.
- KDF-55 (Kinetic Degradation Fluxion).
- Sediment membranes (micro).
- Polypropylene Sediment Filter.
- 2 x Activated Carbon FIlters (double filtration).
- Activated Carbon.
- Micro membrane.
-1st filter: ceramic, activated carbon, ion resin.
-2nd filter: Water Ionizer.
Filters Life (months)6 months / 600 gallons.5 years / 50000 gallons.12 months3 years / 10000 gallons.6 months / 600 gallons.
Water sourceMunicipal water (chlorinated).Municipal water (chlorinated).Both, municipal water (chlorinated) and well water.Municipal water (chlorinated).Municipal Water (Chlorinated).
Warranty1 year.5 Years.1 year.3 years.1 year.
CertifiedNSF/ANSI 42, 53, 401 and P473.NSF/ANSI 42 and 61.NSF/ANSI 42 and 61.NSF/ANSINSF/ANSI 42 and 53.
Read ReviewRead ReviewRead ReviewReview Coming Soon!Review Coming Soon!

Under Sink Water Filter Reviews and Buying Guide Wrap Up

Most water filtration systems have been designed to provide unique benefits.

My believe is that an under sink filter offers some of the qualities of reverse osmosis systems but with the use of similar technology in faucet water filters.

We know there are many other model out there claiming to be the best one you should buy; our advise is to take into account the seven (7) points listed in the “buying the right under counter” section.

Lastly, if you want to explore other alternatives not listed in this under sink water filter guide, I recommend to check our other water filter reviews and guides.


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